The proposed study will use clinical, neuropsychological and neuroradiological techniques to characterize cognitive deficits associated with unipolar and bipolar affective disorder. Specifically, the cognitive deficits associated with major depression and their longitudinal course in bipolar and unipolar affective disorder will be studied. The trait affiliation will be obtained through follow-up retesting and reimaging. The association of these cognitive abnormalities with MRI determined brain abnormalities will be investigated as will the course of the MR abnormalities themselves. To fully characterize the cognitive deficits associated with affective disorder, the extent to which they are similar to cognitive deficits in Huntington's Disease and dissimilar to those of Alzheimer's Disease will be determined. Comparison of structural findings between patients with affective and neurologic illness will be conducted. Based on pilot data and reports of previous investigators, it is predicted that bipolar, and possibly unipolar affective disorder, will be associated with persistent, mild cognitive deficits similar to the subcortical dementia of Huntington's Disease and will be present in conjunction with specific MR abnormalities. The specific MR abnormalities in the affective disorder patient are predicted to be decreased size of neostriata structures and a higher rate of subcortical signal hyperintensities.